You are running two 6770's in Crossfire and your screen is blue? when does it turn blue when you first boot or what? Need more info as to what you have done so far.
Are the 6 pin connecters plug into both cards from your PSU? Is your blue screen have any type of words on it? So lets start with when you first turn on your rig. Run us through the events leading up to the blue screen.
This way we can start with the troubleshooting. But I will leave you with the the Memtest 86+ so you can check your ram if you think it is the problem. Good luck.http://www.memtest.org/